When your application development is completed, you usually will want
to run your Embedded System standalone, i. e.
independent from external resources like NFS filesystems. Instead of
mounting the root filesystem from a remote server you can use a
compressed ramdisk image, which is stored in flash memory and loaded
into RAM when the system boots.

To tell the Linux kernel to use the ramdisk image as root filesystem
you have to modify the command line arguments passed to the kernel,
and pass ramdisk image address as the second argument to the bootm command
(first argument is the memory address of the Linux kernel image, the third
one is the memory address of the flattened device tree blob):